KDM4B and neurodevelopmental disorder: A previous report suggests that JMJD2B is a causative risk gene for neurodevelopmental disorders,8 while accumulating evidence indicates that hippocampal spines in various mouse models of neurodevelopmental disorder are structurally and functionally abnormal.36, 37, 38, 39 For example, mice with a mutation in SHANK2, a risk gene for ASD, display an increased number of hippocampal spines and abnormal synaptic transmission in the hippocampus.37 Furthermore, high-density and spindle-shaped dendritic spines are also observed in the brains of individuals with neurodevelopmental disorders.40